In designing systems using fiber optic lengths, it is frequently necessary to test the operation of various components of the system prior to installation. Previously, to accomplish this in a lab or test facility, it was necessary to provide a full length fiber optic length equilvalent to the actual fiber optic length which is to be used in the installed system. This could be extremely cumbersome since installed systems frequently cover several miles. Thus, the fiber optic length was typically wound on a large mandrel which occupied a great deal of space in the laboratory or test facility.
A related problem in the actual utilization of a system with fiber optic lengths is that single fiber optic lengths frequently must be run parallel to one another. This can create difficulties if the single fiber optic lengths do not have the same degree of attenuation since the output signal of one fiber optic length will differ from the output signal of a parallel length.